Interlock mechanism for lateral file cabinets

ABSTRACT

Interlocks for file cabinets and the like which generally prevent more than one drawer from being opened at a given time. The interlocks include a cable which is changeable from a slack condition to a taut condition. In the taut condition, the interlocks prevent the associated drawer from being opened. In the slack condition, the interlock allows the associated drawer to be opened. The interlocks may be used in conjunction with a lock that selectively changes the tension in the cable from a slack condition to a taut condition and vise versa. The interlocks may be constructed to exert a tension on a cable that is independent of the pulling force exerted on a locked drawer. Alternatively, the interlocks may be constructed to exert a force on the cable that is a small fraction of the pulling force exerted on a locked drawer.

BACKGROUND OF THE INVENTION

The present invention relates to filing cabinets, and more particularlyto mechanisms adapted to prevent one or more of the drawers in thefiling cabinet from being opened. It has been known in the past toinclude interlock mechanisms on filing cabinets that prevent more thanone drawer in the cabinet from being opened at a single time. Theseinterlock mechanisms are generally provided as safety features that areintended to prevent the filing cabinet from accidentally falling over, acondition that may be more likely to occur when more than one drawer inthe cabinet is open. By being able to open only a single drawer at agiven time, the ability to change the weight distribution of the cabinetand its contents is reduced, thereby diminishing the likelihood that thecabinet will fall over.

In addition to such interlocks, past filing cabinets have also includedlocks that prevent any drawers from being opened when the lock is movedto a locking position. These locks are provided to address securityissues, rather than safety issues. These locks override the interlockingsystem so that if the lock is activated, no drawers may be opened atall. If the lock is not activated, the interlock system functions toprevent more than one drawer from being opened at the same time.Oftentimes the system that locks all of the drawers and the interlocksystem that locks all but one of the drawers are at least partiallycombined. The combination of the locking system with the interlockingsystem can provide cost reductions by utilizing common parts.

Past locking and interlocking mechanisms, however, have suffered from anumber of disadvantages. One disadvantage is the difficulty of changingthe drawer configurations within a cabinet. Many filing cabinets aredesigned to allow different numbers of drawers to be housed within thecabinet. For example, in the cabinet depicted in FIG. 1, there are threedrawers in the cabinet. For some cabinets, it would be possible toreplace these three drawers with another number of drawers having thesame total height as the three original drawers. This reconfiguration ofthe drawers is accomplished by removing the drawer slides on each sideof the drawer and either repositioning the drawer slides at the newlydesired heights, or installing new drawer slides at the new heights.Many drawer slides include bayonet features that allow the drawer slidesto be easily removed and repositioned within the cabinet.

In the past, such reconfiguring of the drawers in a cabinet has been adifficult task because the interlocking and/or locking system for thedrawers could not easily be adjusted to match the newly configuredfiling cabinet. For example, U.S. Pat. No. 6,238,024 issued to Sawatzkydiscloses an interlock system that utilizes a series of rigid rods thatare vertically positioned between each drawer in the cabinet. The heightof these rods must be chosen to match the vertical spacing between eachof the drawers in the system. If the cabinet is to be reconfigured, thennew rods will have to be installed that match the height of the newdrawers being installed in the cabinet. Not only does this addadditional cost to the process of reconfiguring the cabinet, itcomplicates the reconfiguring process by requiring new parts of precisedimensions to be ordered. Finding these precisely dimensioned parts mayinvolve extensive searching and/or measuring, especially where themanufacturer of the rods is not the same entity that produced the newdrawers being installed, or the manufacturer of the rods has ceasedproducing the parts, or has gone out of business.

Another difficulty with systems like that disclosed in the Sawatzkypatent is the precise manufacturing that may be required to create theserigid rods. These interlock systems only work if the rods have heightsthat fall within a certain tolerance range. This tolerance range,however, decreases as more interlocks are installed in a given cabinet.In other words, the tolerance of the heights of these rods is additive.In order to function properly, a cabinet with ten drawers will thereforerequire smaller tolerances in the rods than a two drawer cabinet. Inorder to create rods that can be universally used on different cabinets,it is therefore necessary to manufacture the rods within the tighttolerances required by the cabinet having the greatest expected numberof drawers. These tight tolerances tend to increase the cost of themanufacturing process.

Another difficulty with past interlock and lock systems for filecabinets has been the expense involved in creating a locking system thatwill withstand high forces exerted on the drawers. The Business andInstitutional Furniture Manufacturer's Association (BIFMA) recommendsthat lock systems for file cabinets be able to withstand 50 pounds ofpressure on a drawer. Thus, if a file cabinet does not exceed thisstandard, thieves can gain access to the contents of a lock drawer bypulling the drawer outwardly with more than fifty pounds of force. Manyusers of file cabinets, however, desire their locking system to be ableto withstand much greater forces than this before failure. Increasingthe durability of the locking system often adds undesired expense to thecost of building the system.

A number of prior art interlock systems have used cables or straps aspart of the interlocking system. Such systems, however, have sufferedfrom other disadvantages. For example, U.S. Pat. No. 5,199,774 issued toHedinger et al. discloses an interlock and lock system that uses acable. The slack in the cable is decreased when a drawer is opened. Theamount of slack of the cable is carefully chosen during the installationof the drawer lock so that there is just enough slack in the system toallow only one drawer to be opened at a time. The interlock on whateverdrawer is opened takes up this available slack in the cable, whichprevents other drawers from being opened at the same time. A similarsystem is disclosed in U.S. Pat. No. 5,062,678 issued to Westwinkel.This system uses a strap instead of a cable. Both systems suffer fromthe fact that excessive amounts of force may be easily transferred toeither the cable or the strap. In other words, the cable or the strapitself are what resist the pulling force that a person might exert on aclosed drawer when either the lock is activated, or another drawer isopened. The tensile strength of the cable or strap therefore determineshow much force must be exerted to overcome the interlock or lock. Infact, in the interlock of Westwinkel, the system appears to beconstructed so that the pulling force exerted by a person on a lockeddrawer will be amplified before being applied to the strap. The strapmust therefore have a greater tensile strength than the highest ratedpulling force that the lock or interlock system can resist. Increasingthe strength of the cables or straps typically tends to increase theircost, which is desirably avoided.

In light of the foregoing, the desirability of an interlock and locksystem that overcomes these and other disadvantages can be seen.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an interlock and lock thatreduces the aforementioned difficulties, as well as other difficulties.The interlock and lock of the present invention allow relativelylow-tensile strength cables or flexible members to be used in systemswhich provide high resistance to theft and breakdown. The system of thepresent invention further allows changes to cabinet configurations to beeasily implemented with little or no additional work required tointegrate the new cabinet configuration into the interlock or locksystem. The present invention provides a simple construction for locksand interlocks that can be easily manufactured without excessivelyrestrictive tolerances, and which can be easily installed in cabinets.

According to one aspect of the present invention, an interlock for acabinet drawer is provided. The drawer is movable in the cabinet is afirst direction toward an open position and in a second, oppositedirection toward a closed position. The interlock includes an elongated,flexible member, a rotatable lever, an engagement member, and a biasingmember. The lever is adapted to alter the amount of slack in theelongated, flexible member. The lever is rotatable between a firstposition and a second position. The first position creates a low amountof slack in the elongated, flexible member, and the second positionallows a high amount of slack to be present in the elongated, flexiblemember. The engagement member is attached to the drawer and positionedto cause the rotatable lever to rotate toward the first position whenthe drawer is initially moved from the closed position in the firstdirection. The biasing member is positioned adjacent the lever andadapted exert a force that tends to prevent the lever from rotating fromthe first position to the second position until the drawer is moved inthe second direction to the closed position.

According to another aspect of the present invention, an interlock isprovided that includes a cable, a slack take-up mechanism, a cam, and abiasing member. The slack take-up mechanism is engage able with thecable and movable between a high-tension position and a low-tensionposition. The high-tension position creates a greater amount of tensionthan the low-tension position in the cable. The cam is operativelycoupled to the slack take-up mechanism and to the drawer. The cam isadapted to switch the slack take-up mechanism from the low-tensionposition to the high-tension position when the drawer is moved in thefirst direction toward the open position. The biasing member is adaptedto exert a force against the take-up mechanism that urges the slacktake-up mechanism toward the high-tension position. The force of thebiasing member has a magnitude that is independent of the magnitude ofthe force exerted on the drawer in the first direction.

According to still another aspect of the present invention, an interlockis provided. The interlock includes a cable, a rotatable lever, anengagement member, and a retainer. The lever is adapted to change thecable between high and low slack conditions. The engagement member isattached to the drawer and positioned to cause the lever to rotate to afirst position that changes the cable to a low slack condition when thedrawer is initially moved in the first direction from the closedposition. The engagement member is also positioned such that a firstforce exerted on the drawer in the first direction is translated by thelever to a second force on the cable, which is less than the firstforce. The retainer is adapted to retain the rotatable lever in thefirst position while the drawer is moved to the open position.

According to still another aspect of the present invention, a lockingand interlocking system for a cabinet is provided. The system includes alock, a first cable, a second cable, a first interlock, and a secondinterlock. The first cable extends between at least a first and seconddrawer. The first cable is changeable from a high slack to a low slackcondition. The second cable extends between the lock and the firstdrawer. The lock is adapted to change the second cable from a high slackto a low slack condition. The first interlock is in communication withthe first and second cables and adapted to change both said first andsaid second cables from the high slack to the low slack conditionwhenever the first drawer is opened. The first interlock is furtheradapted to prevent the first drawer from opening whenever the first orsecond cables are in the low slack condition. The second interlock is incommunication with the first cable and adapted to change the first cablefrom the high slack to the low slack condition whenever the seconddrawer is opened. The second interlock is further adapted to prevent thesecond drawer from opening whenever the first cable is in the low slackcondition.

According to yet another aspect of the present invention, a cabinet isprovided that includes at least one drawer movable within the cabinet ina first direction toward an open position and in a second, oppositedirection toward a closed position. The cabinet further includes a frameadapted to support the drawer, an elongated, flexible member, aninterlock, and a slack take up mechanism. The elongated, flexible memberis positioned within the cabinet and changeable between a lower slackcondition and a higher slack condition. The interlock is positionedwithin the frame and in operative engagement with the elongated,flexible member. The interlock is adapted to prevent the drawer frommoving to the open position when the elongated, flexible member is inthe lower slack condition and to allow the drawer to move to the openposition when the elongated, flexible member is in the hither slackcondition. The slack take up mechanism is adapted to change theelongated, flexible member from the high slack condition to the lowerslack condition when the drawer is moved from the closed position to theopen position. The slack take up mechanism is further adapted totranslate a first force exerted on the drawer in the first direction toa second force exerted on the elongated, flexible member which is lessthan the first force.

According to still other aspects of the present invention, the interlockmay be in communication with a lock that is adapted to selectively alterthe condition of the cable. The interlocks may be secured to drawerslides that are removable from the cabinet. A cable guide may beincluded as part of the interlock to snap fittingly receive the cableand retain it in engagement with the interlock.

The various aspects of the present invention provides an interlock andlock system that is versatile, resistant to high forces, and easilyinstalled. These and other benefits of the present invention will beapparent to one skilled in the art in light of the following writtendescription when read in conjunction with the accompanying drawings. Theinterlock may be in communication with a lock that is adapted toselectively alter the tension in the cable.

The interlocks may be secured to drawer slides that are removable fromthe cabinet. A cable guide may be included as part of the interlock tosnap-fittingly receive the cable and retain it in engagement with theinterlock.

The various aspect of the present invention provides an interlock andlock system that is versatile, resistant to high forces, and easilyinstalled. These and other benefits of the present invention will beapparent to one skilled in the art in light of the following writtendescription when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cabinet with three drawers in a closedposition;

FIG. 2 is a perspective view of the cabinet of FIG. 1 illustrated withone drawer moved to an open position;

FIG. 3 is a side, elevational view of an interlock and drawer slideaccording to a first embodiment of the present invention;

FIG. 4 is a perspective view of a pair of interlocks according to thefirst embodiment of the present invention;

FIG. 5 is a side, elevational view of the pair of interlocks of FIG. 4;

FIG. 6 is a perspective, exploded view of the interlock of FIG. 3;

FIG. 7 is a perspective view of the interlock of FIG. 3 illustratedwithout a drawer slide attached;

FIG. 8 is a perspective view of an attachment plate of the interlock ofFIG. 3;

FIG. 9 is a plan view the attachment plate of FIG. 8;

FIG. 10 is a side, elevational view of the attachment plate of FIG. 8;

FIG. 11 is a perspective view of a sliding plate of the interlock ofFIG. 3;

FIG. 12 is a plan view of the sliding plate of FIG. 11;

FIG. 13 is a side, elevational view of the sliding plate of FIG. 11;

FIG. 14 is a perspective view of a cam of the interlock of FIG. 3;

FIG. 15 is a plan view of the cam of FIG. 14;

FIG. 16 is a side, elevational view of the cam of FIG. 14;

FIG. 17 is a perspective view of an engagement member of the interlockof FIG. 3;

FIG. 18 is a front, elevational view of the engagement member of FIG.17;

FIG. 19 is a perspective view of a rivet of the interlock of FIG. 3;

FIG. 20 is a side, elevational view of a spring of the interlock of FIG.3;

FIG. 21 is a perspective view of a cable guide of the interlock of FIG.3;

FIG. 22 is a bottom view of the cable guide of FIG. 2E;

FIG. 23 is a plan view of the cable guide of FIG. 21;

FIG. 24 is a side, elevational view of the interlock and drawer slide ofFIG. 3 illustrated with the interlock in a locked position;

FIG. 25 is a side, elevational view of the drawer slide and interlock ofFIG. 3 illustrating the interlock in a position in which two drawers arebeing simultaneously pulled toward an open position;

FIG. 26 is a side, elevational view of the drawer slide and interlock ofFIG. 3 illustrating the interlock in an open position with the drawerslide contacting the CAM;

FIG. 27 is a side, elevational view of the drawer slide and interlock ofFIG. 3 illustrating the interlock in an unlocked position, and thedrawer slide disengaged from the cam;

FIG. 28 is a side, devotional view of a drawer slide and interlockaccording to a second embodiment of the present invention;

FIG. 29 is a bottom view of the drawer slide and interlock of FIG. 28;

FIG. 30 is a side, elevational view of the drawer slide and interlock ofFIG. 28 taken from a side opposite to that of FIG. 28;

FIG. 31 is a front, elevational view of the interlock of FIG. 28;

FIG. 32 is a perspective, exploded view of the components of theinterlock of FIG. 28;

FIG. 33 is a perspective view of a lever of the interlock of FIG. 28;

FIG. 34 is a plan view of the lever of FIG. 33;

FIG. 35 is a side, elevational view of the lever of FIG. 33;

FIG. 36 is a perspective view of a cam of the interlock of FIG. 28;

FIG. 37 is a side, elevational view of the cam of FIG. 36;

FIG. 38 is a plan view of the cam of FIG. 36;

FIG. 39 is a side, elevational view of the cam of FIG. 36 taken from aside different from that of FIG. 37;

FIG. 40 is a perspective view of a cable guide of the interlock of FIG.28;

FIG. 41 is a front, elevational view of the cable guide of FIG. 40;

FIG. 42 is a bottom view of the cable guide of FIG. 40;

FIG. 43 is a partial, perspective view of a drawer slide member with anengagement member for engaging the interlock of FIG. 28;

FIG. 44 is a side, elevational view of the spring of the interlock ofFIG. 28;

FIG. 45 is a perspective view of a rivet of the interlock of FIG. 28;

FIG. 46 is a perspective view of another rivet of the interlock of FIG.28;

FIG. 47 is a side, elevational view of the interlock of FIG. 28illustrated in a lock position.

FIG. 48 is a side, elevational view of the interlock of FIG. 28illustrated in a position in which two drawers are being simultaneouslypulled toward the open position;

FIG. 49 is a side, elevational view of the interlock of FIG. 28illustrating the interlock in an unlocked position with the engagementmember in contact with the cam;

FIG. 50 is a side, elevational view of the interlock of FIG. 28illustrated in an unlocked position in which the engagement member ofthe slide has moved out of engagement of the cam;

FIG. 51 is a perspective view of a lock illustrated in a lockedposition;

FIG. 52 is a side, elevational view of the lock of FIG. 51;

FIG. 53 is a perspective view of the lock of FIG. 51 illustrated in anunlocked position;

FIG. 54 is a side, elevational view of the lock of FIG. 53;

FIG. 55 is a perspective, exploded view of the lock of FIG. 51; and

FIG. 56 is a side, sectional view of a cabinet and interlock systemaccording to one aspect of the present invention;

FIG. 57 is a side, elevational view of a drawer slide and interlockaccording to another embodiment of the present invention;

FIG. 58 is an enlarged end view of the drawer slide and interlock ofFIG. 57;

FIG. 59 is an enlarged view of the drawer slide and interlock of FIG. 57illustrating the interlock in a locked position;

FIG. 60 is an enlarged view of the drawer slide and interlock of FIG. 57illustrating the interlock in an unlocked position with the engagementmember in contact with the cam; and

FIG. 61 is an enlarged view of the drawer slide and interlock of FIG. 57illustrating the interlock in an unlocked position in which theengagement member of the slide has moved out of engagement of the cam.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to theaccompanying drawings wherein the reference numerals in the followingwritten description correspond to like numbered elements in the severaldrawings. The present invention relates to locks and interlocks that maybe used with file cabinets, such as the file cabinet 60 depicted inFIGS. 1 and 2. File cabinet 60 includes three drawers 62 a-c that areessentially stacked on top of each other in file cabinet 60. Each drawercan be pulled in a first direction 64 toward an open position. The lowermost drawer 62 c in FIG. 2 is illustrated in the open position. When itis time to close this drawer, it can be pushed in a second direction 66back to its closed position. The interlocking system of the presentinvention prevents more than one drawer from being opened at a singletime. While only three drawers are illustrated in file cabinet 60, thepresent invention is applicable to cabinets having any number ofdrawers. The present invention also includes a locking system thatoverrides the interlocking system. That is, when the locking system isactivated, no drawers can be opened at any time. When the locking systemis deactivated, the interlocking system is activated and prevents morethan one drawer from being opened at a single time. The locking systemmay be activated by inserting a key into a keyhole 68 positioned at anysuitable location on the file cabinet. The locking and interlockingsystem are highly integrated so that many of the components of theinterlocking system are also used in the locking system.

The interlocks of the present invention may be advantageously combinedor attached to the drawer slides in which drawers 62 slidingly movebetween their open and closed position. An example of one of thesedrawer slides 70 is depicted in FIG. 2 for the lowermost drawer 62 c.Each drawer 62 includes two drawer slides 70, one positioned on one sideof the drawer and another positioned on the opposite side of the drawer.While the interlocks of the present invention can be placed at otherlocations besides on drawer slide 70, the attachment of the interlocksto the drawer slide 70 allows the interlocks to be simultaneouslyremoved and repositioned when the drawer slides 70 are removed andrepositioned. This greatly facilitates the reconfiguration of a filecabinet 60 with differently sized drawers 62.

An interlock 72 according to a first embodiment of the present inventionis depicted in FIG. 3, Interlock 72 is attached to a drawer slide 70.Interlock 72 is operatively coupled to a cable 74 that runs verticallyinside of cabinet 60. In general, interlock 72 operates according to thetension in cable 74. Specifically, cable 74 has two different basiclevels of tension. When no drawers are opened and the lock is notactivated, cable 74 has a first amount of tension in it. When a singledrawer is opened, interlock 72 takes up the slack in cable 74 andcreates a second level of tension in cable 74. With the second level oftension, the slack in cable 74 is reduced to such a small level that noother drawers in the cabinet 60 can be opened. When the open drawer isclosed, the slack in the cable 74 returns and any other single drawermay thereafter be opened. If a lock is included with the cabinet 60, thelock is adapted to alter the tension in cable 74. When in the lockedposition, the lock removes the slack in cable 74. When in the unlockedcondition, the lock provides cable 74 with sufficient slack so that asingle drawer may be opened. Interlocks 72 are thus designed to onlyallow their associated drawer to be opened when cable 74 has sufficientslack. Further, they are designed to remove the slack in cable 74, iftheir associated drawer is opened. The detailed construction ofinterlock 72, as well as how they accomplish the aforementionedfunctions, will now be described.

As illustrated in FIG. 6, interlock 72 generally includes an attachmentplate 76, a sliding plate 78, a rotatable cam or lever 80, a spring 82,a cable guide 84, an engagement member 86, and a rivet 88. Attachmentplate 76 is a stationary part that secures interlock 72 to drawer slide70. Specifically, attachment plate 76 is secured to a stationary portion90 of drawer slide 70. Stationary portion 90 is illustrated in FIGS. 4and 5. Stationary portion 90 is, in turn, secured to appropriateattachment structures within file cabinet 60. Those attachmentstructures may allow drawer slide 70 to be easily removed andrepositioned inside of cabinet 60. Attachment plate 76 may be secured tostationary portion 90 of drawer slide 70 in any suitable fashion, suchas by welding, or the use of fasteners.

Attachment plate 76 includes a plurality of fastener holes 92 which maybe used to receive rivets, screws, or other fasteners to secureattachment plate 76 to stationary portion 90 of drawer slide 70.Attachment plate 76 is depicted in detail in FIGS. 6 and 8-10.Attachment plate 76 further includes a rivet hole 94 which receivesrivet 88. Rivet 88 secures cam 80 to attachment plate 76 in a rotatablefashion. Stated alternatively, cam 80 is attached to attachment plate 76in such a manner that it can rotate about the axis generally defined byrivet 88. Attachment plate 76 further includes a spring attachment nub96 to which one end of spring 82 is attached. Attachment plate 76 alsoincludes a pair of bent flanges 98. Bent flanges 98 are received insideof cable guide 84 and used to secure cable guide 84 to attachment plate76. Each flange 98 includes a shoulder 100 that retains cable guide 84on attachment plate 76 after they have been attached, as will beexplained in more detail below.

Sliding plate 78, which is depicted in detail in FIGS. 6 and 11-13, ispositioned between attachment plate 76 and cam 80. Sliding plate 78slides linearly in a direction parallel to first and second directions64 and 66. When a drawer 62 is initially opened, sliding plate 78 slideslinearly in first direction 64. As the drawer fully closes, slidingplate 78 slides back to its original position in second direction 66.Sliding plate 78 includes an elongated aperture 102 that receives rivet88. Because elongated aperture 102 has a length much greater than thediameter of rivet 88, sliding plate 78 can slide along rivet 88 whilestill being supported by rivet 88. Sliding plate 78 includes anengagement lug 104 positioned at an end generally opposite to elongatedaperture 102. Engagement lug 104 engages cable 74 generally along itsside that faces toward elongated aperture 102. The side of sliding plate78 adjacent engagement lug 104 is supported in a channel 106 defined bycable guide 84. When sliding plate 78 slides in first direction 64,engagement lug 104, which is in engagement with cable 74, decreases theslack in cable 74. Thus, when a drawer is open, sliding plate 78 andengagement lug 104 remove the slack from cable 74. This will bedescribed in more detail below.

Sliding plate 78 further includes a spring attachment nub 108. Springattachment nub 108 is used to attach the other end of spring 82 tosliding plate 78. When spring 82 is connected between attachment nubs108 and 96, spring 82 exerts a force that tends to urge attachment nubs96 and 108 toward each other in a direction generally parallel to firstdirection 64. The movement of sliding plate 78 toward spring attachmentnub 96 of attachment plate 76 is limited by an interior surface 110 ofelongated aperture 102. When interior surface 110 contacts rivet 88,sliding plate 78 can no hanger be moved any further in first direction64. As will be described in more detail herein, spring 82 exerts thetensioning force on cable 74, by way of engagement lug 104 when a draweris opened. Depending on the physical construction of interlock 72, aswell as the type of cable 74 chosen, spring 82 may be desirably chosento exert a force against sliding plate 78 of one to two pounds in afirst direction 64 when a drawer is open. Other amounts of force canalso be used within the scope of the present invention. The amount ofthis force should be sufficient to retain cable 74 in a taut conditionwhenever any other drawers are attempted to be opened.

Sliding plate 78 further includes an embossment 112 on a side 114 thatfaces cam 80. Embossment 112 is positioned between elongated aperture102 and engagement lug 104. Embossment 112 interacts with cam 80 in amanner that will be described in more detail herein. In general, cam 80acts as a switch for moving sliding plate 78 between a tensioningposition, in which tension is exerted on cable 74, and a non-tensioningposition, in which no tension, or very little tension, is exerted oncable 74. This switching occurs when the drawer associated withinterlock 72 is opened or closed. This switching utilized embossment112, as explained more below.

Cam 80, which is depicted in more detail in FIGS. 6 and 14-16, includesa central aperture 116 which receives rivet 88. As mentioned previously,cam 88 is rotatable about rivet 88. Cam 80 includes a pair of spacedflanges 118 that define a channel 120 therebetween. Channel 120selectively receives engagement member 86. Engagement member 86 isattached to the drawer 62 such that it will move linearly in firstdirection 64 when the drawer is open, and in second direction 66 whenthe drawer is closed. Cam 80 translates this linear motion into arotational motion. Cam 80 includes a first surface 122 that engagesembossment 112 whenever the associated drawer is fully closed. Raisedshoulders 124 a and b are defined adjacent each end of first surface122. Raised shoulders 124 a and b tend to maintain embossment 112 onfirst surface 112 and thereby resist inadvertent rotation of cam 80.

From the position illustrated in FIG. 6, cam 80 is generally rotatablein a direction 126. This rotation in direction 126 is activated by theassociated drawer being pulled toward the open position. When the draweris so pulled, engagement member 86 begins to move in first direction 64.Because engagement member 86 is housed within channel 120, this movementin first direction 64 causes cam 80 to begin to rotate in direction 126.As this rotation continues, raised shoulder 124 a of cam 80 comes intocontact with embossment 112. In order for the rotation of cam 80 tocontinue, sliding plate 78 must be pushed in second direction 66 a smallamount in order to provide clearance for embossment 112 to overcomeshoulder 124 a. Shoulder 124 a is an optional feature that, if provided,helps to ensure that the drawer stays shut after it is closed. If thedrawer is shut hard enough to create a rebounding force that wouldotherwise cause the drawer to open backup again, at least partially,shoulder 124 a provides sufficient resistance to prevent this reboundingforce to open the drawer. Shoulder 124 a thus serves to maintain adrawer in the closed position until a user exerts sufficient force on adrawer to move embossment 112 past shoulder 124 a.

After embossment 112 has overcome raised shoulder 124 a, the force ofspring 82 tends to pull sliding plate 78 in first direction 64. If cable74 is in a taut condition, however, sliding plate 78 will not be able tomove in first direction 64 because engagement lug 104 will be preventedfrom moving in first direction 64 by the taut cable. If the cable istaut, further rotation of cam 80 in direction 126 will only be able tocontinue until a stop surface 128 on cam 80 abuts against embossment112. This condition is illustrated in FIG. 7. Once stop surface 128comes into contact with embossment 112, further rotation of cam 80indirection 126 is impossible. The degree of rotation of cam 80 whenembossment 112 is in engagement with stop surface 128 is insufficient toallow engagement member 86 to exit from channel 120. If a personattempts to open the associated drawer, the force they exert in thefirst direction will be transferred from engagement member 86 to cam 80.Cam 80 will transfer this force to embossment 112 via its contact withstop surface 128. Due to the construction of cam 80, the force exertedby stop surface 128 against embossment 112 will generally be a verticalforce that is perpendicular to first direction 64. The force exerted onsliding plate 78 through embossment 112 will therefore not tend to movesliding plate 78 in either first direction 64 or second direction 66.The pressure of stop surface 128 against embossment 112 will thereforenot create any forces on engagement lug 104. Cable 74 is thereforeshielded from the forces exerted on the drawer when the cable is in ataut condition.

If cable 74 is not in a taut condition when cam 80 rotates in direction126, then sliding plate 78 will be free to move in first direction 64after embossment 112 has cleared raised shoulder 124 a. This movement ofsliding plate 78 in first direction 64 will cause embossment 112 to alsomove in first direction 64. This movement of embossment 112 will allowit to fit into a channel 130 defined on cam 80. Channel 130 is suitablydimensioned to allow cam 80 to continue to rotate until channel 120 isangled enough to, allow engagement member 86 to exit channel 120. Thus,the drawer can be opened. The movement of embossment 117 into channel130, which is caused by the biasing force of spring 82, will also causeengagement lug 104 to move in first direction 64. The movement ofengagement lug 104 in first direction 64 will increase the tension incable 74 to a taut condition. No other drawers will therefore be able tobe opened simultaneously.

When the associated drawer is closed, engagement member will cause cam80 to rotate in a direction opposite to the direction of its rotationwhen the drawer is opened. This closing rotation will cause a surface131 on cam 80 to engage embossment 112. This engagement pushesembossment 112, and consequently sliding plate 74 in second direction66. In order to avoid requiring excessive force to close the drawer,surface 131 may be angled at about 45 degrees when it contactsembossment 112. This allows sliding plate 78 to be pushed in seconddirection 66 without excessive forces.

Engagement member 86, which is depicted in more detail in FIG. 17, isattached to an elongated member 132. Elongated member 132 is fixedlysecured to the drawer. Elongated member 132 is positioned on top of thedrawer slide 70. Elongated member 132 includes various apertures thatmay be used to secure it to the drawer 62. Elongated member 132 includesa lower flange 134 that may be used to mount member 132 to drawer slide70 (FIG. 18). Rivet 88 and spring 82 are depicted in FIGS. 19 and 20,respectively.

Cable guide 84, which is depicted in more detail in FIGS. 21-23 servesto ensure that cable 74 is properly maintained in contact withengagement lug 104 of sliding plate 78. Cable guide 74 may bemanufactured of molded plastic. Cable guide 84 preferably snap-fittinglyreceives cable 84 so that cable 74 may be easily threaded into guide 84with little danger of cable 74 becoming unthreaded. Cable guide 84includes an upper and lower portion 136 a and b. Channel 106 is definedbetween upper and lower portions 136 a and b. As has been described,channel 106 provides clearance for sliding plate 78 and engagement lug104. Cable guide 84 includes two glide surfaces 138 that provide supportto sliding plate 78. Each portion 136 a and b further includes anaperture 140. Apertures 140 receive bent flanges 98 of attachment plate76 when cable guide 84 is attached thereto.

Apertures 140 are spaced apart in a vertical direction a distance thatis slightly smaller than the vertical distance between shoulders 100 onflanges 98 of attachment plate 76. Thus, when flanges 98 are insertedinto apertures 140, shoulders 100 contact and press against innersurfaces 142 of apertures 140. The dimensions of shoulders 100 forceinner surfaces 142 to flex inwardly towards each other. When flanges 98have been completely inserted into apertures 140, shoulders 100 havemoved past inner surfaces 142, allowing them to flexibly snap back totheir unstressed position. Shoulders 100 contact surfaces 144 of cableguide 84. Shoulders 100 thus prevent flanges 98 from being retracted outof apertures 140 without flexing inner surfaces 142 towards each other.Because shoulders 100 do not have a cam surface that facilitates removalof flanges 98 from apertures 140, cable guide 84 is securely retained onflanges 98 of attachment plate 76.

Cable 74 is easily threaded into cable guide 84 by moving cable 74 indirection 146 into channel 106 (FIG. 21). Movement of cable 74 in thisdirection causes the cable 74 to come in contact with two flexible arms148. As cable 74 is further pushed against flexible arms 148, flexiblearms 148 begin to flex out of the way until sufficient clearance isprovided for cable 74 to pass by flexible arms 148. As soon as cable 74passes by arms 148, they snap back to their unflexed condition. In thisunflexed condition, cable 74 is prevented from being retracted out ofchannel 106 in a direction opposite the direction 146 by flexible arms148. If an interlock 72 is to be removed from the inside of a cabinet,cable 74 can be easily removed from cable guide 84 by manually pressingflexible arms 148 in direction 146. Flexible arms 148 are pressed untilsufficient clearance is provided for cable 74 to be retracted out ofguide 84 in a direction generally opposite to direction 146.

FIGS. 4 and 5 illustrate a pair of interlocks 72 a and 72 b in differentconditions. The cable 74 in FIGS. 4 and 5 is in a taut condition. Thedrawer that is attached to the drawer slide of interlock 72 b is in aclosed position. As has been described previously, first surface 122 ofcam 80 is in contact with embossment 112 in this position. The drawercorresponding to interlock 72 a illustrates the condition of interlock72 a when this drawer is trying to be opened and cable 74 is already ina taut condition due to either a lock or another interlock with itsdrawer open (not shown). Because cable 74 is in a taut condition,engagement lug 104 of sliding plate 78 (of interlock 72 a) is preventedfrom moving further in first direction 64 than that illustrated in FIGS.4 and 5. Because sliding plate 78 cannot move further in first direction64, embossment 112 of sliding plate 78 cannot move out of the way ofstop surface 128 on cam 80. Embossment 112 thus prevents cam 80 fromfurther rotation while cable 74 is in the taut condition. Because cam 80cannot rotate any further, engagement member 86 cannot disengage fromchannel 120 of cam 80. The drawer therefore cannot be opened. As noted,cable 74 of FIGS. 4 and 5 is in the taut condition due to anotherinterlock with an opened drawer (not shown) that is in communicationwith cable 74. Alternatively, cable 74 could be in the taut conditionbecause it is in communication with a lock that is moved to the lockingposition. FIG. 7 also illustrates an interlock 72 for a drawer that istrying to be opened when cable 74 is in the taut condition. Again, thetaut condition of cable 74 is due to either a lock or another interlockthat is not shown in FIG. 7.

FIGS. 3 and 24-27 illustrate interlock 72 in its various positionsaccording to different drawer conditions. FIG. 3 illustrates interlock72 when the associated drawer is closed. FIG. 24 illustrates interlock72 when the cable 74 has been changed to the taut condition by anun-illustrated interlock or lock and the drawer associated withinterlock 72 is trying to be pulled open. The drawer is prevented frombeing opened by the engagement of stop surface 128 with embossment 112.Because stop surface 128 presses vertically down on embossment 112,sliding plate 78 does not experience a linear force in either first orsecond direction 64 or 66. Whatever force is exerted against the drawerin first direction 64 is therefore not translated to cable 74. Rather,cable 74 only experiences a tensioning force from interlock 72 that isdue to spring 82 acting to pull engagement lug 104 in first direction64. The tensile strength of cable 74 therefore does not appreciablylimit the amount of force that can be applied to trying to open thelocked door before the interlock system fails. Interlock 72 of thepresent invention may resist up to 150 pounds of force on a drawer, ormore, before it fails. Further, this failure point will be due to cam 80and its interaction with either embossment 112 or engagement member 86,not the tensile strength of cable 74. Interlock 72 thus shields cable 74from the forces that are applied in first direction 64 to open lockeddrawers.

FIG. 25 depicts interlock 72 in the position it would move to when aperson was trying to simultaneously open two drawers in the cabinet.Because no single drawer is fully open, cable 74 includes sufficientslack to allow embossment 112 to almost move past stop surface 128.However, embossment 112 cannot totally clear stop surface 128, andneither drawer will be able to be opened in this situation due to thepartial engagement of stop surface 128 with embossment 112.

FIG. 26 illustrates an interlock 72 in which the drawer associated withinterlock 72 is partially open. As can be seen, embossment 112 has movedinto channel 130 of cam 80. This has allowed cam 80 to rotatesufficiently to allow engagement member 86 to disengage from cam 80. Thecomplete disengagement of engagement member 86 from cam 80 isillustrated in FIG. 27. FIG. 27 illustrates the condition of interlock72 when the drawer is open to a greater extent than that depicted inFIG. 26. When the drawer of interlock 72 is moved back to its closestposition, cam 80 must be oriented so that engagement member 86 can slideback into channel 120. In order to prevent cam 80 from inadvertentlyrotating out of this orientation while the drawer is fully opened, cam80 can be appropriately weighted so that it is unlikely to rotate whenengagement member 86 is disengaged. This weighting can be adjusted bycutting holes in cam 80 at appropriate locations to remove weight, suchas hole 127 (FIGS. 14-16). Another flange, such as flange 129 (FIGS.14-16) may also be added to increase the weight of cam 80 on a selectedside of its pivot axis. Flange 129 may also be used to provideadditional structural strength to cam 80 to help resist excessivepulling forces from engagement number 86 when the drawer is locked, butbeing attempted to be opened.

An interlock 72′ according to a second embodiment of the presentinvention is depicted, either partially or wholly, in FIGS. 28-50.Interlock 72′, like interlock 72, is adapted to be attached directly toa drawer slide 70′. While both interlocks 72 and 72′ are depictedattached to the back ends of drawer slides 70 and 70′, it will beappreciated that they can be attached to the drawer slides at anydesirable location along the drawer slides' length. Interlock 72′operates in conjunction with a cable 74 in a similar manner thatinterlock 72 operates. Specifically, interlock 72′ allows only a singledrawer to be open at a given time. If a lock is included in the cabinet,the lock is in communication with cable 74 and can change the amount ofslack in cable 74. If the lock is activated, cable 74 has little or noslack, and none of the drawers may be opened. Interlock 72′ differs frominterlock 72 in that a small portion of the pulling force exerted on adrawer in first direction 64 is transmitted to cable 74. Nevertheless,the amount of force transmitted is so small that a cable 74 having arelatively low tensile strength can still be used in a cabinet whichprovides strong resistance to its locking system being overcome.

Interlock 72′ operates according to the same general principal asinterlock 72 and is operatively coupled to a cable 74 that runsvertically inside of cabinet 60. Specifically, cable 74 is installedwithin the cabinet with a certain amount of slack. In general, interlock72′ operates according to the amount of slack in cable 74. When thefirst drawer of the cabinet is opened, the associated interlock 72′removes the slack from cable 74. As long as this drawer remains open,cable 74 remains in a low slack condition. The low slack condition ofcable 74 prevents any other drawers from simultaneously being opened.When the one drawer is closed, cable 74 returns to its slack condition.In other words, cable 74 has two different basic levels of slack. When asingle drawer is opened, interlock 72′ takes up most of or all the slackin the cable 74 and creates a second, lower level of slack in cable 74.The lower level of slack in cable 74 is such that no other drawers inthe cabinet can be opened. This lower level of slack may be zero, or maybe a small amount of slack. When the drawer is closed, more slack in thecable returns. At that point, any other single drawer may be opened, orthe same drawer may be opened again. If a lock is included, the lock isadapted to alter the slack in cable 74 when the lock is activated. Inthis activated state, no drawers may be opened in the cabinet. When inthe unlocked condition, the lock allows cable 74 to have sufficientslack so that a single drawer may be opened. Interlocks 72′ are thusdesigned to only allow their associated or attached drawer to be openedwhen cable 74 has sufficient slack. Further, they are designed to removesubstantially all of the slack in cable 74, if their associated draweris opened. The detailed construction and operation of interlock 72′ willnow be described.

For purposes of description, components of interlock 72′ that aresimilar to components in interlock 72 will be described with the samereference numeral followed by the prime (C) symbol. Components ofinterlock 72′ that are substantially different from components ofinterlock 72 will be described with a completely new reference numeral.As can be easily seen in FIG. 32, interlock 72′ is attached tostationary portion 90′ of drawer slide 70′. Stationary portion 90′ isfixedly secured to the interior of cabinet 60. Stationary portion 90′includes an upper aperture 150 and a lower aperture 152. Upper aperture150 receives a first rivet 154 that pivotally secures a lever 156 tostationary portion 90′. Lower aperture 152 receives a second rivet 158that pivotally secures a cam 160 to stationary portion 90′. Interlock72′ further includes a cable guide 84′ that is mounted to a pair offlanges 98′ on stationary portion 90′ in generally the same manner thatcable guide 84 is mounted to attachment plate 76 of interlock 72.Interlock 72′ further includes a spring 82′ and an engagement member86′. Engagement member 86′ comprises a flange 162 that extends off of aslidable portion 164 of drawer slide 70′. Slidable portion 164 isslidable with respect to stationary portion 90′ by way of a plurality ofball bearing cages 166 that house a plurality of ball bearings incontact with both slidable portion 164 and stationary portion 90′ ofdrawer slide 70′ (FIGS. 28-29). Slidable portion 164 is adapted to besecured to a drawer. Slidable portion 164 may include a plurality ofattachment flanges 168 used to releasably secure slidable portion 164 tothe drawer. Similarly, stationary portion 90′ may also include aplurality of attachment flanges 170 used to releasably secure stationaryportion 90′ to the interior of the cabinet.

Lever 156, which is illustrated in more detail in FIGS. 32-35, ispivotable about a pivot axis generally defined by first rivet 154. Lever156 includes an aperture 172 for receiving first rivet 154. Lever 156includes a spring attachment nub 174 over which one end of spring 82′ issecured. Lever 156 further includes an engagement lug 104′ that engagescable 74. When lever 156 rotates about its pivot axis 176 in a direction178 (FIG. 32), engagement lug 104′ pulls against cable 74 decreasing theslack in cable 74. Spring 82′ exerts a force on lever 156 that tends toresist rotation in direction 178.

Lever 156 includes an inner surface portion 180 and a crest 182. When adrawer is initially opened, cam 160 abuts against crest 182 and exerts arotational force on lever 156. If cable 74 is not in a low slackcondition, cam 160 pushes against crest 182 until lever 156 is rotatedsufficiently to put cam 160 in contact with inner surface portion 180.This will be described in more detail below.

Cam 160, which is depicted in detail in FIGS. 32 and 36-39, isrotationally secured to stationary portion 90′ of drawer slide 70′ byway of second rivet 158. Cam 160 includes a recess 184 into whichengagement member 86′ fits when the associated drawer is in the closedposition. Recess 184 includes a contact surface 186 that contactsengagement member 86′ when the associated drawer is pulled in the firstdirection 64. When a drawer is pulled in first direction 64, engagementmember 86′ engages contact surface 186 and imparts a rotational force oncam 160. This rotational force is generally in the direction 188 (FIG.32). Rotational direction 188 is the opposite of rotational direction178. The rotation of cam 160 in direction 188 causes an edge 190 of cam160 to press against crest 182 of lever 156. If sufficient rotationalforce is exerted on cam 160, edge 190 will push against lever 156sufficiently to allow edge 190 to pass by the crest 182 on lever 156.Crest 182 may have an arced or radial surface that allows edge 190 toovercome it without a excessive force spike.

The rotation of cam 160 in direction 188 causes lever 156 to rotate indirection 178 (FIG. 32). The rotation of lever 156 takes up any slack incable 74 by way of engagement member 86′. If cable 74 is already in alow slack condition, lever 156 will be prevented from rotatingsufficiently far enough to allow edge 190 of cam 160 to reach innersurface portion 180 of lever 156. The full rotation of cam 160 willtherefore be prevented. Engagement member 86′ of slidable portion 164 ofdrawer slide 70′ will therefore not be able to disengage from recess 184in cam 160. Drawer slide 70′ will therefore not be able to slide, andthe attached drawer will not be able to open.

When cable 74 is changed to a low slack condition by another interlockor lock, cam 160 cannot rotate further than the position depicted inFIG. 31. If cable 74 is not already in a low slack condition, then cam160 will be able to rotate sufficiently far so that edge 190 contactsinner surface portion 180. When edge 190 is in contact with innersurface 180, cam 160 has rotated sufficiently far to allow engagementmember 86′ to disengage out of recess 184. Slide 70′ is therefore freeto slide and the attached drawer can be fully opened. When the drawer isfully open, spring 82′ exerts a force on lever 156 in a directionopposite to rotational direction 178. This rotational force tends tomaintain edge 190 in frictional contact with inner surface portion 180.This rotational force tends to maintain edge 190 in frictional contactwith inner surface portion 180. This prevents edge 190 from sliding backto contact with crest 182 before the drawer is fully closed, and thismaintains cam 160 in the proper rotational altitude for recess 184 toaccept engagement member 86′. When the drawer is being closed,engagement member 86′ eventually comes into contact with a contactsurface 194 defined on cam 160. As the drawer is fully closed,engagement member 86′ pushes against contact surface 194 to therebycause cam 160 to rotate in a rotational direction that is opposite todirection 188. This rotation causes edge 190 to move out of contact withsurface portion 180 and into contact with crest 182. This, in turn,allows lever 156 to rotate in a direction opposite to direction 178.This rotation causes engagement lug 104′ to decrease the force on cable74. The closing of the drawer therefore decreases any tension in cable74 and increases its slack.

In addition, to maintain cam 160 in its proper rotational orientationwhen a drawer is opened, spring 82′ helps prevent the drawers fromrebounding open, or partially open, after they are slammed shut. Withoutspring 82′, it might be possible for a drawer to be slammed shut withsufficient force such that the rebound of the drawer in first direction64 might rotate earn 160 and allow the drawer to open up again. Spring82′ helps prevent such rebounding of the drawers into the open positionby biasing lever 156 in a direction that resists the rotation of cam160. The amount of biasing is sufficient to generally overcome theamount of force typically present in a drawer rebound. The drawerstherefore do not rebound open, but rather only open when a user appliessufficient force to overcome the biasing resistance that spring 82′exerts.

Cam 160 includes a sloped surface 196 that helps ensure that engagementmember 86′ is successfully guided back into recess 184 when a drawer isclosed. If engagement member 86′ contacts sloped surface 196, it willexert a rotational force on cam 160 that tends to rotate cam 160 so thatrecess 184 is properly aligned for receiving engagement member 86′. Cam160 further includes chamfered surfaces 198 a and b. Chamfered surfaces198 a and 198 b are designed to urge slidable portion 164 of drawerslide 70′ into proper axial alignment with cam 160. Statedalternatively, if slidably portion 164 of drawer slide 70′ is compressedtoward stationary portion 90′, chamfered surface 198 will contact an endflange 200 on slidable portion 164 and urge it away from stationaryportion 90′ (FIG. 32). Second chamfered surface 198 b will continue tourge slidable portion 164 away from stationary portion 90′ as the draweris completely closed. Chamfered surfaces 198 a and b therefore serve tohelp maintain the proper spacing of stationary portion 90′ with respectto slidable portion 164.

Cam 160 further includes a slide surface 202 that contacts a respectiveslide surface 204 on lever 156 (FIGS. 33-39). Slide surfaces 202 and 204help ensure that cam 160 and lever 156 maintain the proper axialposition with respect to each other as they are rotated. Edge 190 of cam160 may preferably be arced with a radius of 0.04 inches. Crest 182 mayalso be arced with a radius of 0.06 inches. Other values may, of course,be used. Rounding edge 190 and crest 182 reduces the amount of forcenecessary to open the drawer. However, rounding these surfacesexcessively will cause more of the force exerted on a locked drawer tobe transferred to the cable 74.

Cable guide 84′, which is depicted in detail in FIGS. 40-42, serves toensure that cable 74 is properly maintained in contact with engagementlug 104′ of lever 156. Cable guide 74 may be manufactured of moldedplastic. Cable guide 84′ preferably snap-fittingly receives cable 84′ sothat cable 74 may be easily threaded into guide 84′ with little dangerof cable 74 becoming unthreaded. Cable guide 84′ includes an upper andlower portion 136 a and 136 b. A channel 106 is defined between upperand lower portions 136 a and 136 b.

Cable 74 is easily threaded into cable guide 84′ by moving cable 74 indirection 146 into channel 106 (FIG. 40). Movement of cable 74 in thisdirection causes the cable 74 to come in contact with two flexible arms148. As cable 74 is further pushed against flexible arms 148, flexiblearms 148 begin to flex out of the way until sufficient clearance isprovided for cable 74 to pass by flexible arms 148. As soon as cable 74passes by arms 148, they snapback to their unflexed condition. In thisunflexed condition, cable 74 is prevented from being retracted out ofcable guide 74 in a direction opposite the direction 146 by flexibleantis 148. If an interlock 72 is to be removed from the inside of acabinet, cable 74 can be easily removed from cable guide 84′ by manuallypressing flexible arms 148 in direction 146. Flexible arms 148 arepressed until sufficient clearance is provided for cable 74 to beretracted out of guide 84′ in a direction generally opposite todirection 146. Cable guide 84′ includes a spring attachment nub 206 thatholds an end of spring 82′ opposite spring attachment nub 174 on lever156. Cable guide 84′ includes recesses (not shown) that receive flanges98′ and that interact with the shoulders 100′ to secure guide 84′ tostationary portion 90′. These recesses are defined on the bottom ofcable guide 84′ and do not extend all the way through cable guide 84.Shoulders 100 abut against surfaces 144 when cable guide 84′ is attachedto stationary member 90′ (FIG. 42).

FIG. 43 depicts slidable portion 164 of drawer slide 70′ in more detail.FIG. 44 depicts spring 82′ in more detail. FIGS. 45 and 46 depict firstand second rivets 154 and 158 respectively. Second rivet 158 includes asloped undersurface 159 (FIG. 45) that helps to maintain slideableportion 164 of the drawer slide, as well as the attached drawer, inproper alignment with the stationary portion 90′. If the drawer issubjected to pulling forces, or other types of forces, that tend tocause the drawer to rack or twist (especially if made out of thin sheetmetal), these forces may move the back end of slideable portion 164 awayfrom stationary portion 90′. In such instances, end flange 200 will comeinto contact with sloped undersurface 159 of rivet 158 as the drawer isclosed. The sloped nature of surface 159 will create a force on endflange 200 of slideable portion 164 that pushes the back end ofslideable portion 164 toward stationary portion 90′ in a directiongenerally parallel to pivot axis 176. This helps maintain the properalignment of the drawer when it is closed. End flange 200 may bechamfered to correspond to the angle of undersurface 159 in order tomore easily force the drawer into the proper alignment. Undersurface 159also helps to ensure that engagement member 86′ stays aligned with cam160 so that engagement member 86′ properly engages cam 160. Withoutrivet 158 and undersurface 159, it might be possible for a drawer tobecome excessively racked such that engagement member 86′ no longercontacted cam 160 when the drawer was opened and closed. Undersurface159 prevents this possibility.

The head of rivet 158 preferably does not extend farther away from thestationary portion 90 than does slidable portion 164. Rivet 158,therefore, does not obstruct the drawer attached to slidable portion 164and the back end of the drawer may extend all the way back to the backend of the drawer slide. Interlock 72, therefore, does not put any spacelimitations on the dimensions of the drawer other than those required bythe drawer slide.

As mentioned previously, interlock 72′ is designed to transfer only asmall fraction of a pulling force exerted on a drawer onto cable 74.This reduction in forces can best be understood with reference to FIG.31. FIG. 31 illustrates interlock 70′ in the position it would be inwhen the attached drawer is being pulled in the open direction whilecable 74 is in a taut or low slack condition. The tautness of cable 74prevents interlock 70 from allowing the drawer to be opened. FIG. 31depicts interlock 72′ with slidable portion 164 and second rivet 158removed in order to illustrate the underlying structure. Line 208represents the moment arm of cam 160 as it pivots about its pivot point210 (corresponding to the center of rivet 158). Line 212 represents themoment arm of lever 156 as it pivots about its pivot point 214(corresponding to the center of rivet 154). For purposes of discussingthe forces applied to interlock 72′, it will be assumed that the cable74 depicted in FIG. 31 is already in a low slack condition due to eitheran associated lock being activated, or another interlock having allowedanother drawer to be opened. Interlock 72′ depicted in FIG. 31 thereforemust prevent its attached drawer from opening in order to functionproperly. If a person exerts a strong pulling force on the drawerattached to interlock 72′ of FIG. 31, this force will be greatly reducedwhen it is eventually applied to cable 74. The pulling force exerted onthe drawer in first direction 64 is transmitted to cam 160 by engagementmember 86′. Engagement member 86′ engages cam 160 generally in recess184. The pulling force exerted on the drawer, which is illustrated bythe arrow F_(D), acts on moment arm 208 at a point D. This pointcorresponds to the location where engagement member 86′ contacts firstsurface 186 of recess 184. Force F_(D) will cause cam 160 to rotategenerally in a counter clock-wise direction, as depicted in FIG. 31.This rotation will cause edge 190 of cam 160 to push against crest 182of lever 156 with a force of F_(C). F_(C) refers to the amount of forceexerted by cam 160 on lever 156. Because force F_(C) will be applied bycam 160 at a location that is farther away from pivot point 210 onmoment arm 208, force F_(C) will be less than force F_(D).

The force F_(C) will be applied to moment arm 212 of lever 156 at aposition C. Position C is located on moment arm 212 at a position thatis relatively close to pivot point 214. Force F_(C) will be transferredvia lever 156 to cable 74 at a point T. Point T refers to the positionwhere engagement lug 104′ engages cable 74. Because point T issubstantially farther away from pivot point 214 along moment arm 212,the magnitude of force F_(T) will be significantly less than themagnitude of force F_(C). Further, the spring 81′ will exert a forceF_(S) along lever 156 at a point S. This force F_(S) acts in oppositionto the force F_(T). Because point S is farther away from pivot point 214along moment arm 212, a smaller amount of force F_(S) is necessary tocancel out the force F_(T). The force F_(T) that is exerted againstcable 74 will therefore be greatly reduced as compared to the forceF_(D) that is exerted on the drawer. The tensioning force F_(T) may beas little as 1/20th, or less, of the magnitude of the force F_(D). Cable74 can therefore resist drawer-pulling forces that greatly exceed itsmaximum tensile strength.

In addition to transferring only a fraction of the force of F_(D) tocable 74, the arrangement of cam 160 and lever 156 also magnifies themovement of engagement lug 104′ with respect to the rotation of cam 160.Stated alternatively, if the attached drawer is moved in first direction64 a small distance A that causes cam 160 to partially rotate, thedistance that engagement lug 104′ moves in first direction 64 will begreater than the distance A. For example, if the drawer is moved infirst direction 64 for 0.05 inches, this may cause engagement lug 104′to move 0.65 inches. This feature decreases the amount of movement inthe locked drawers that might otherwise be present. A drawer that islocked will therefore only be able to be pulled a small distance beforetaut cable 74 prevents it from being opened. Interlock 72′ can thusprevent drawers from being opened even for the small distance that mightotherwise easily allow an intruder to insert a screw driver, or otherlever mechanism, between the drawer and the cabinet.

FIGS. 47-50 depict interlock 72′ in several different states. In FIG.47, interlock 72′ is in the position it would be if someone were pullingon the attached drawer while the cable 74 (not shown) was in a low slackcondition. The cable 74 would therefore prevent cam 160 in lever 156 ofinterlock 72′ from rotating further than that depicted in FIG. 47. FIG.48 depicts the position of interlock 72′ when the drawer is trying to bepulled open simultaneously with another drawer. When two drawers aretrying to be opened simultaneously, lever 156 can rotate more than itcan in FIG. 47. However, the rotation of lever 156 is insufficient toallow edge 190 of cam 160 to travel past crest 182. Cam 160 thereforedoes not rotate sufficiently to allow engagement lever 86′ to disengagefrom recess 184. Therefore, neither drawer being simultaneously pulledwill allow it to be opened.

FIG. 49 depicts interlock 72′ in its condition when engagement member86′ has just begun to disengage from recess 184. Engagement member 86′has moved to a greater extent than in FIGS. 47 and 48. This greatermovement creates sufficient force against cable 74 (not shown) to putthe cable in a low slack condition, thereby preventing other drawersfrom being opened simultaneously. With surface 190 in contact withsurface 180, lever 156 is prevented from rotating back, therebymaintaining cable 74 in the lower slack state when another drawer isattempted to be opened. FIG. 50 depicts an interlock 72′ in which thedrawer has opened sufficiently far to disengage engagement member 86′from recess 184.

An example of a lock 216 that may be used in conjunction with thepresent invention is depicted in FIGS. 51-55. Lock 216 selectivelychanges the condition of cable 74 from a low slack condition to a lowslack condition. Lock 216 includes a hole 260, which may be a keyhole,into which a key may be inserted or which may receive a bar that iscoupled to a conventional lock cylinder. If hole 260 is a keyhole,insertion of the proper key therein allows a key cylinder 218 to berotated by the key. If hole 260 received a bar, which may be desirablewhere lock 216 is positioned at the back end of the cabinet, the bar iscoupled to any conventional lock in a manner that causes the bar to beable to rotate about its longitudinal axis when the proper key isinserted into the conventional lock. In either situation, key cylinder218 therefore will rotate when a proper key is used. Key cylinder 218includes a pin 220 that moves in a cam track 222 defined in areciprocating member 224. Reciprocating member 224 is snap-fittinglyattached to a cover 226 by way of a flexible arm 228. Flexible arm 228fits into an aperture 230 defined in cover 226. Flexible arm 228includes a shoulder 232 that retains reciprocating member 224 to cover226 when the two are snap fit together. The snap fitting occurs whenflexible arm 228 initially contacts cover 226. A cam surface 234 causesflexible arm 228 to flex as reciprocating member 224 is initially pushedtoward cover 226. After the two are completely secured together,flexible arm 228 snaps back to its unflexed condition in which shoulder232 prevents the two members from being separated.

Reciprocating member 224 includes a pair of apertures 236. Cable 74 maybe secured to one of the apertures 236. When key cylinder 218 is rotatedtoward a locking condition, reciprocating member 224 moves verticallyupward with respect to cover 226 (FIGS. 51-52). This vertical movementdecreases the slack in cable 74 such that no drawers in the cabinet maybe opened. When lock 216 is unlocked, the unlocking rotation of keycylinder 218 moves reciprocating member 224 vertically downward withrespect to cover 226 (FIGS. 53-54). This creates sufficient slack incable 74 for a single drawer to be opened. Cover 226 may be securelyfastened inside of cabinet 60 in any suitable manner.

Cable 74 may be secured to one of apertures 236 by threading the cabletherethrough and tying it, such as is illustrated in FIGS. 51-54.Alternatively, a more preferred method of securing cable 74 to apertures236 is accomplished by way of a 7-hook 300 (FIG. 55). J-hook 300 iscrimped onto an end of cable 74 in a conventional manner. J-hook 300includes a lower vertical section 302, a middle horizontal section 304,and an upper vertical section 306. Upper vertical section 306, alongwith a portion of horizontal section 304, is inserted through one ofapertures 236 and manipulated until upper vertical section 306 contactsone side of the wall in which apertures 236 are defined and is orientedvertically. In this position, horizontal section 304 passes horizontallythrough the aperture 236 and lower vertical section 302 abuts against aside of the wall in which aperture 236 is defined that is opposite theside contacting upper section 306. In this position, J-hook 300 ismaintained in aperture 236 and can only be released by manually twisting7-hook 300 appropriately to allow upper section 306 to be backed out ofaperture 236. 7-hook 300 thus provides a convenient way for installingand removing cable 74 from lock 216.

The opposite end of cable 74 may also be fastened within a cabinet byusing a J-hook that fits through an aperture attached to the cabinet,although any other method of securing cable 74 can be used with thepresent invention. If it is desired to avoid having an end of cable 74be attached to the frame of the cabinet, it could alternatively be heldin place by interacting with cable guide 84′. Specifically, an enlargedring or other structure could be affixed to the end of the cable. Thisenlarged structure would be dimensioned so that it was too large to passthrough the cable passageway defined in cable guide 84. For securing thebottom of the cable, the enlarged structure would thus abut against abottom surface 310 of the lower-most cable guide 84′ (FIGS. 40-42). Ifit were desired to secure the top end of the cable in a like manner to acable guide 84′, rather than to a lock 216, an enlarged structure couldalso be attached to the top end of cable 74. In this situation, theenlarged structure would abut against a top surface 312 of the uppermostcable guide 84′. The enlarged structure may preferably be shaped to snaponto, or otherwise be secured to, cable guide 84′. If an enlargedstructure were used on both ends of the cable to secure it in thecabinet, the proper cable slack could be set by manufacturing the cableto the specific length that created the desired amount of slack.

Lock 216 could be modified so that reciprocating member 224 utilized aspring or other structure that selectively increased or decreased thetension on cable 74. In other words, rather than having reciprocatingmember 224 absolutely move to is raised position when the key is rotatedto the locked position, lock 216 could be modified to include a spring,or other biasing force, that urged member 224 towards its upper, lockedposition. If no drawers were open, this biasing force would besufficient to raise member 224 to its locked position. If one drawerwere open, this biasing force would be insufficient to move the member224 to its upper position because the cable would be in its low slackcondition, thereby preventing member 224 from moving upward while thedrawer was opened. As soon as a drawer was closed, however, the biasingforce would move member 224 to is locked position and remove the slackin the cable that was created by the drawer closing.

This arrangement allows the lock to be switched to the locked positionwhile a drawer is still open. Once the drawer closed, it wouldimmediately be locked and not able to be opened until the lock 216 wasdeactivated. The modified lock 216 thus would allow the cabinet to belocked while a drawer was still open, and as soon as the open drawer wasclosed, it would immediately lock. Thereafter, no drawers could beopened until the lock was deactivated. The biasing force exerted onreciprocating member 224 in modified lock 216 should be sufficient toremove the slack in cable 74 when all the drawers are closed and tomaintain the cable in the locked, low slack condition when pullingforces are exerted against one or more locked drawers.

Lock 216 may be further modified to include a solenoid, or otherelectrically controlled switch, that controls the movement ofreciprocating member 224 between its locked and unlocked position. Thesolenoid could be controlled remotely by a user using a hand-held devicethat transmitted wireless signals to a receiver in the cabinet thatcontrolled the solenoid. The control could be carried out in aconventional manner, such as in the manner in which remote, keylessentry systems work on many current automobiles. Alternately, the cabinetcould include a keypad, or other input device, in which the locking orunlocking of the cabinet was controlled by information, such as a codeor password, input by a user.

A single interlock 72′ is all that is needed for each drawer in thecabinet. The opposite drawer slide can thus be a regular drawer slidewith no interlock attached. Interlock 72, of course, can be attacheddirectly to the cabinet, rather than integrated with the drawer slide.During the installation of the interlock system into a cabinet, theslack in the cable maybe easily set by securing one end of the cable,opening a single drawer, and then pulling the cable until substantiallyall of its slack is removed. The cable is then secured in thatcondition. When the drawer is thereafter closed, the cable will havesufficient slack to allow only a single drawer to be opened at a time.Alternatively, cables 74 could be manufactured at a preset length to fitdifferent cabinet heights. The installer of the interlocks thereforecould simply fasten the cable in the desired location and the length ofthe cable will create the appropriate slack to allow a single drawer tobe opened. Once the appropriate length of a cable is determined for agiven cabinet height, cables could be easily mass-produced by amanufacturer by simply cutting them to the appropriate lengths.

An interlock system 240 is depicted in FIG. 56. Interlock system 240 isdepicted on cabinet 60, which includes three drawers 62 a-62 c.Interlock system 240 includes three interlocks 72. It should beunderstood that interlocks 72 may be replaced with interlocks 72′ (orinterlocks 472 described below). An upper lock 216 a and a lower lock216 b are included. Upper lock 216 a is adapted to selectively lock theuppermost two drawers 62 a and 62 b. Lower lock 216 b is adapted toselectively lock the lower drawer 62 c. An interlock cable 74 a extendsvertically within cabinet 60 and runs through each of the interlocks 72for each of the drawers 62 a-c. Cable 74 a is attached within thecabinet at attachment points 242, which may utilize J-hooks 300, or anyother suitable means, for attaching cable 74 a within cabinet 60. Thesealternative means may include a screw, a bolt, or other means. An uppercable 74 b runs vertically from upper lock 216 a through the twointerlocks 72 of the uppermost two drawers 62 a and b. The lower end ofupper cable 74 b is secured at an attachment point 244, which may bepositioned above lowermost drawer 262 c. Alternatively, attachment point244 may be positioned below drawer 62 c, but cable 74 b should not runthrough interlock 72 of lowermost drawer 62 c. Lower cable 74 c extendsvertically from lower lock 216 b to the bottom of cabinet 60. Lowercable 74 c is secured to the bottom of cabinet 60 at an attachment point74 c. The interlock 72 of upper drawer 62 a and b thus have two cables74 a and b passing through them. Cable 74 a and b may be threadedthrough interlock 72 in the same manner as has been describedpreviously. Specifically, both cables 74 a and b may be threaded throughcable guides 84 and around engagement lug 104.

When either cable 74 a or 74 b is in the low slack condition, interlock72 will prevent the associated drawers 62 a or b from being opened. Ifboth cables 74 a and b are in the low slack condition, interlock 72 willalso, of course, prevent the associated drawers 62 a or b from beingopened. Because cable 72 a also runs through the interlock associatedwith the lowermost drawer 62 c, only one drawer in the entire cabinetmay be opened at a given time. Cable 74 c, which runs through theinterlock 72 of the lowermost drawer 62 c, allows the lowermost drawer62 e to be selectively locked independently of the locking of theuppermost two drawers 62 a and b. Cables 74 a and c, which run throughinterlock 72 of the lowermost drawer 62 c, may be run side by sidethrough interlock 72 in the same manner that has been described above.Alternatively, an additional engagement lug 104 may be provided on allof the interlocks that extends outwardly in an opposite direction toengagement lug 104. Cable guide 84 may be modified to include a secondchannel to accommodate the second cable and align it with the addedengagement lug. Other modifications may be made to accommodate thesecond cable. System 240 allows the two upper drawers to be lockedindependently of the lower-most drawer while only a single drawer may beopened at any time if either or both of the locks are not activated.

An interlock 472 according to yet another embodiment of the presentinvention is depicted in FIGS. 57-61. Though many parts of interlock 472are similar to the previous embodiments, the numbers have been changedfor clarity, except for cable 74. Interlock 472 is attached to a drawerslide 470 and operatively coupled to a cable 74 (FIGS. 59-61) that runsvertically inside of the cabinet. In general, similar to previousembodiments, interlock 472 operates according to the amount of slack incable 74. When no drawers are opened and the lock is not activated,cable 74 has a high amount of stack in it. When a single drawer isopened, interlock 472 takes up most or all of the slack in cable 74 andcreates a second, lower level of slack in cable 74. The lower level ofslack in cable 74 is such that no other drawers in the cabinet can beopened. This lower level of slack may be zero, or may include a smallamount of slack. When the open drawer is closed, more slack in the cable74 returns and any other single drawer may thereafter be opened. If alock is included with the cabinet, the lock is adapted to alter theslack in cable 74. When in the locked position, the lock removes most orall of the slack in cable 74. When in the unlocked condition, the lockallows cable 74 to have sufficient slack so that a single drawer may beopened. Interlocks 472 are thus designed to only allow their associatedor attached drawer to be opened when cable 74 has sufficient slack.Further, they are designed to remove substantially all of the slack incable 74, if their associated drawer is opened. The detailedconstruction of interlock 472 will now be described below. For detailsof suitable locks, reference is made to the description provided above.

Interlock 472 is adapted to be attached directly to a drawer slide 470.While interlock 472 is depicted attached to the back end of the drawerslide, it will be appreciated that it can be attached to a drawer slideat any desirable location along the drawer slide's length. Alternately,the interlock can be attached directly to the cabinet. Interlock 472operates in conjunction with cable 74 so that only a single drawer canbe open at a given time. As understood from FIGS. 59-61, interlock 472is attached to stationary portion 490 of drawer slide 470. Stationaryportion 490 is fixedly secured to the interior of the cabinet.Stationary portion 490 includes a first aperture 450 and a secondaperture 452 (FIG. 61). Aperture 450 receives a first rivet 454 thatpivotally secures a lever 456 to stationary portion 490. Aperture 452receives a second rivet 458 that pivotally secures a cam 460 tostationary portion 490. Interlock 472 further includes a cable guide484, which is similar to cable guide 84′ described in reference to theprevious embodiment. Therefore for further details for cable guidereference is made to previous embodiments. Guide 484 is mounted to aflange (not shown) on stationary portion 490 in generally the samemanner that cable guide 84 is mounted to attachment plate 76 ofinterlock 72. Interlock 472 further includes a spring 462 (shown inphantom in FIG. 61) and an engagement member 486.

Spring 462 mounts on one end to the lever 456 at a stop 462 a and on itsother end to fixed rail 490 in a manner to urge lever 456 to move in acounter-clockwise direction about rivet 454 (as viewed in FIGS. 59-61).However, when, as will be more fully described below, the drawer isextended from the cabinet, lever 454 will compress spring 462 under theinfluence of cam 460 and will pull on cable 74 so that cable 74 is in alow slack condition (FIG. 61). In the illustrated embodiment, engagementmember 486 comprises an elongate aperture or slot 486 a formed in theweb 464 a of slidable portion 464 of drawer slide 470. Slidable portion464 is slidable with respect to stationary portion 490 by way of aplurality of bearings 466, such as ball bearing cages that house aplurality of ball bearings, which are in contact with both slidableportion 464 and stationary portion 490 of drawer slide 470 (FIG. 58).Slidable portion 464 is adapted to be secured to a drawer. Slidableportion 464 may include one or more attachment flanges 468 forreleasably securing slidable portion 464 to the drawer. Similarly,stationary portion 490 may also include one or more attachment flanges570 used to releasably secure stationary portion 490 to the interior ofthe cabinet.

Lever 456 is pivotable about a pivot axis generally defined by firstrivet 454. Lever 456 includes an aperture for receiving first rivet 454,similar to the previous embodiments. As noted above, lever 456 includesa spring attachment tab or nub 462 a to which one end of the spring issecured and an engagement lug 404 that engages cable 74. When lever 456rotates about its pivot axis in a clockwise direction (as viewed inFIGS. 59-61), engagement lug 404 pulls against cable 74 decreasing theslack in cable 74. Spring 462 exerts a force on lever 456 that tends toresist this rotation and is compressed when lever 456 rotates to pull oncable 74.

Similar to the previous embodiments, lever 456 includes an inner surfaceportion 480, which optionally defines the range of motion of cam 460.When a drawer is initially opened, cam 460 rotates counterclockwise andexerts a rotational force on lever 456. If cable 74 is not in a lowslack condition, surface portion 492 of cam 460 pushes against innersurface portion 480 until lever 456 is rotated sufficiently to removethe slack.

Cam 460 is rotationally secured to stationary portion 490 of drawerslide 470 by way of second rivet 458. Cam 460 includes an engagementsurface 584, such as a pin 584 a, with which engagement member 486 isengaged when the associated drawer is in the closed position. Pin 584 acontacts engagement member 486 when the associated drawer is pulled inan extended or first direction. When a drawer is pulled in the extendeddirection, engagement member 486 engages pin 584 a and imparts arotational force on cam 460. The shape of aperture 486 a is such that asthe drawer is extended, pin 584 a is urged downward (as viewed in FIG.60) to pivot cam 460 in a counterclockwise direction (as viewed in FIG.60). The rotation of cam 460 in this direction causes a surface portion492 of cam 460 (FIG. 61) to rotate lever 456 in a counterclockwisedirection and, thereby, compress spring 462.

This rotation of lever 456 takes up any slack in cable 74 by way ofengagement lug 404. However, if cable 74 is already in a low slackcondition, lever 456 will be prevented from rotating sufficiently sothat full rotation of cam 460 will therefore be prevented. Engagementmember 486 of slidable portion 464 of drawer slide 470 wilt thereforenot be able to disengage from pin 584 a of cam 460. Drawer slide 470will therefore not be able to slide, and the attached drawer will not beable to open.

When cable 74 is changed to the low slack condition by another interlockor lock, cam 460 cannot rotate further. If cable 74 is not already in alow slack condition, then cam 460 will be able to rotate sufficiently toallow engagement member 486 to disengage from pin 584 a. Slide 470 istherefore free to slide and the attached drawer can be fully opened.When the drawer is fully open, the spring 462 exerts a force on lever456 in a direction opposite its clockwise rotational direction, whichtends to maintain the surface portion 492 of cam 460 in frictionalcontact with inner surface portion 480 of lever 456. This maintains cam460 in the proper rotational attitude for pin 584 a to be engaged byengagement member 486. When the drawer is being closed, engagementmember 486 comes into contact with pin 584 a on cam 460. As the draweris fully closed, engagement member 486 pushes against pin 584 a tothereby cause cam 460 to rotate in a clockwise direction (as viewed fromFIG. 60 to FIG. 59). This rotation causes surface portion 492 of cam 460to move along inner surface portion 480. This, in turn, allows lever 456to rotate in a counterclockwise direction (as viewed in FIGS. 60 and61). This rotation causes engagement lug 404 to decrease the force oncable 74. The closing of the drawer therefore decreases any tension incable 74 and increases its slack.

In addition to maintaining cam 460 in its proper rotational orientationwhen a drawer is opened, spring 462 helps prevent the drawers fromrebounding open, or partially open, after they are slammed shut. Withoutthe spring, it might be possible for a drawer to be slammed shut withsufficient force such that the rebound of the drawer might rotate thecam and allow the drawer to open up again. The spring helps prevent suchrebounding of the drawers into the open position by biasing the lever ina direction that resists the rotation of the cam, as noted in referenceto the previous embodiment.

Referring to FIGS. 59-61, engagement member 486 includes a slopedsurface 496 that helps ensure that pin 584 a is successfully guided backinto recess 586 a when a drawer is closed. If pin 584 a contacts slopedsurface 496, it will exert a rotational force on cam 460 that tends torotate cam 460 so that pin 584 a is properly aligned to extend intorecess 486 a. For further details of lever 456 and the interaction withcam 460, reference is made to the lever and cam of interlock 72′.

FIGS. 59-61 depict interlock 472 in several different states. In FIG.59, interlock 472 is in the position it would be if the drawer isclosed. FIG. 60 illustrates the interlock if someone were pulling on theattached drawer while the cable 74 (not shown) was in a high slackcondition when engagement member 486 has just begun to disengage frompin 584 a. FIG. 61 depicts an interlock 472 in which the drawer hasopened sufficiently far to disengage engagement member 486 from pin 584a.

While other materials may be used, the interlocks described herein maybe made primarily of metal. Specifically, the attachment plates, slidingplates, cams, and rivets may all be made of metal, such as steel, or anyother suitable metal. The engagement members may be made of metal or anyother suitable material. The cable guides may be all made from plastic.The drawer slides are preferably made of metal, such as steel, with theexception of the ball bearing cages for the ball bearings, which may bemade of plastic. The levers, cams, and cable guides of interlock 72′ orinterlock 472 may all be made of plastic. The first and second rivets,stationary portion, and slidable portion may also all be made of metal,such as steel. Spring 82 of interlock 72 may exert a force of 1.5pounds. The springs of interlock 72′ and 472 may exert a force ofapproximately 0.5 pounds. Other spring strengths may, of course, beused. The cables may comprise steel cables each composed of sevenstrands, with each strand made of seven individual filaments and mayhave a tensile strength of 40 pounds. The cables may preferably be madeof stainless steel and include a vinyl coating. For example, thediameter of the cable after coating may be 0.024 inches, although otherdimensions can be used. To avoid kinking of the cables, surfaces thatcome in contact with the cable, such as the engagement lug, may becurved with a radius of at least 0.125 inches to help reduce thepossibility of kinking. As several possible alternatives to steel, thecable could be a string, a plastic based line, such as those used asfishing lines, or any other elongated, flexible member with suitabletensile strength.

While the present invention has been described in terms of the preferredembodiments depicted in the drawings and discussed in the abovespecification, it will be understood by one skilled in the art that thepresent invention is not limited to these particular preferredembodiments, but includes any and all such modifications that are withinthe spirit and scope of the present invention as defined in thefollowing claims.

1. An interlock for a drawer positionable within a cabinet, the drawerbeing movable in the cabinet in a first direction toward an openposition and in a second, opposite direction toward a closed position,said interlock comprising: an elongated, flexible member; a rotatablelever adapted to switch the amount of slack in said elongated, flexiblemember between a low slack condition and a high slack condition byrotating between a first and second position, respectively; a rotatableengagement member that is rotatable relative to the rotatable lever andis positioned to cause said rotatable lever to rotate toward said firstposition when said drawer is initially moved from the closed position inthe first direction.
 2. The interlock of claim 1 further comprising abiasing member positioned adjacent said lever, said biasing memberadapted to exert a biasing force that tends to prevent said lever fromrotating from said second position to said first position until saiddrawer is moved in said first direction to the open position.
 3. Theinterlock of claim 1 wherein said elongated, flexible member is a cable.4. The interlock of claim 3 further including a cable guide adapted tosnap-fittingly receive the cable from at least one direction.
 5. Theinterlock of claim 1 wherein said elongated, flexible member is incommunication with at least one other rotatable lever associated withanother drawer, said at least one other rotatable lever adapted tochange said elongated, flexible member from the high slack to the lowslack condition when the at least one other drawer is moved to an openposition.
 6. The interlock of claim 1 wherein said elongated, flexiblemember is in communication with a lock, said lock adapted to selectivelychange said elongated, flexible member between said low and high slackconditions.
 7. The interlock of claim 6 further including a second,elongated flexible member in communication with a second lock and saidlever, said second lock adapted to selectively change said secondelongated, flexible member between said low and high slack conditions.8. The interlock of claim 1 wherein said lever is to be mounted on adrawer slide member.
 9. The interlock of claim 8 wherein said interlockis to be solely mounted to said drawer slide member.
 10. The interlockof claim 1 wherein said rotatable lever is configured to translate afirst force exerted on the drawer in the first direction into a secondforce exerted against said elongated, flexible member that is less thansaid first force.
 11. The interlock of claim 10 wherein said secondforce is less than one-half of said first force.
 12. An interlock for adrawer positionable within a cabinet, the drawer being movable in thecabinet in a first direction toward an open position and in a second,opposite direction toward a closed position, said interlock comprising:an elongated, flexible member adapted to be changeable between a highslack condition and a low slack condition; a cam member having a drivingsurface, and having a projection that communicates with a slot in adrawer slide member; an actuating member positioned to be operativelyengageable with said elongated, flexible member, and engageable with thecam driving surface, said actuating member adapted to change saidelongated, flexible member to said low slack position when the drawer isopened and to allow said elongated flexible member to exist in said highslack condition when the drawer is closed; and wherein the actuatingmember moves via the cam drive surface with the cam being moved via theprojection being engaged with the slot in the drawer slide member. 13.The interlock of claim 12 wherein the actuating member further comprisesa rotatable lever.
 14. The interlock of claim 12 wherein the cam memberis rotatable.
 15. The interlock of claim 12 further comprising a springthat exerts a force on said actuating member.
 16. The interlock of claim12 wherein the actuating member is adapted to move a distance withrespect to the elongated, flexible member at least five times greaterthan the distance the drawer moves when initially being moved toward anopen position.
 17. The interlock of claim 12 wherein the cam member isto be mounted on a drawer slide member.
 18. The interlock of claim 12wherein the interlock is to be mounted on a drawer slide.
 19. Theinterlock of claim 12 wherein the actuating member is adapted to movewith respect to the elongated, flexible member faster than the drivingsurface moves when the drawer is initially being moved toward an openposition.
 20. An interlock for a drawer positionable within a cabinet,the drawer being movable in the cabinet in a first direction toward anopen position and in a second, opposite direction toward a closedposition, said interlock comprising: an elongated, flexible member; arotatable lever adapted to switch the amount of slack in said elongated,flexible member between a low slack condition and a high slack conditionby rotating between a first and second position, respectively; anengagement member positioned to cause said rotatable lever to rotatetoward said first position when said drawer is initially moved from theclosed position in the first direction; wherein said engagement memberfurther comprises a projection that communicates with a slot in a drawerslide member; and wherein the rotatable lever moves via the engagementmember with the engagement member being moved via the projection beingengaged with the slot in the drawer slide member.
 21. The interlock ofclaim 20 wherein said interlock is to be solely mounted to a drawerslide having said drawer slide member.